This invention concerns an electric cable barrier gland.
This invention has particular application to cable barrier glands of the type that are fitted to an electric cable to provide a barrier to prevent ingress of liquid, gas or solids into the interstices of the cable between the cable cores when the cable sheathing has been removed to enable the connection of the conductive elements of the cable cores to some electrical equipment or installation. Barrier glands of this type are commonly used in hazardous locations and must meet specific flameproof performance criteria to prevent the risk of explosion.
It is already known to provide such a cable barrier gland in which a hardenable compound is used to fill the interstices between the cable cores and this compound is confined within a liner, sleeve or pot through which the cores extend. Such barrier glands with filler compounds and sleeves or pots are known, and two particular arrangements are described in our GB Patents Nos. 2104306 and 2060281.
The manufacture of barrier glands requires accurate and close machining or production as there are prescribed limitations on any gap between unthreaded surfaces in a cable gland. Such gap is commonly referred to as the flame gap and requirements in cable glands are specified in British Standards No. 4683 and No. 5501 of 1971 (Parts 1 and 5) as well as in other Standards issued by regulatory or approval testing authorities.
In our GB Patent No. 2104306 we proposed to overcome certain problems relating to the tolerances required by using a deformable sleeve or lining into which the hardenable material is packed to provide the barrier seal around the cores. The arrangement is such that the deformable sleeve or lining is intended to expand radially on assembly and compression of the gland so that the sleeve or lining is forced into sealing engagement with the complementary unthreaded part of the gland to ensure that there is no flame path. However, in use of the compound material, this presents difficulties in the field because such compound is normally made up from two separate materials which have to be mixed together, one being a resin and the other being a catalyst hardener. The mixture is of a putty-like consistency but ambient temperature variations effect consistency and hardening or curing times, and handling of the materials may be under adverse or extraordinary field conditions.
When a deformable sleeve or lining is used in a gland and subject to filling with a compound, local deformation of the sleeve may arise presenting problems during assembly. In addition, the compound may be spread over the external face of the sleeve or lining during assembly and restrict adequate sealing engagement on completion and compression of the gland.
It is an object of this invention to provide an improved electric cable barrier gland by the construction of which such difficulties can be alleviated in a simple and effective manner.